A voice coil motor, a spindle motor or a stepping motor is used to position or rotate an object. A motor driving circuit adjusts power supplied to a motor through a feedback control such that a detecting signal indicating a current state of the motor reaches a command value indicating a target state of the motor.
Such a motor driving scheme may be generally classified into a linear driving type and a switching driving type. For the switch-driving type, a pulsed driving voltage having a switching frequency is supplied to a motor. In the motor driving circuit, the switching frequency is frequently set to an out-of audible band, for example, about 50 kHz in order to limit sound noises.
In motor driving circuits of the switch-driving type, the following problem may occur. Specifically, it has been found that, even when the switching frequency is set to the out-of audible band, an effective frequency of the pulsed driving voltage falls within an audible band due to a response delay of an error amplifier disposed in a feedback loop, which may result in audible noises.